First full month has passed with our 8kW Daikin Althema HP.
We haven’t changed anything else in the house.
Thanks to the info and help from this site we’ve got things pretty much set up as we like them and economically too!
The tweaks of going LWT (with set temp set back scheduling) and getting the ECO hot water heating scheduling functioning like clockwork, have really helped our daily COPs.
Early in the month we were a bit all over the place on the Madoka, and the Comfort hot water setting really isn’t very efficient.
According to the MMI in Feb 2025 we used 510kWh for heating and hot water.
Comparing avg gas usage for previous February’s going back to 2016, we used ~1904kWh.
Ratio elec to gas 3.7.
Our total Feb bill was a bit lower than it would have been on gas!
Our gas tariff is 5.91p/kW (we fixed last year) so ~£120 for for the month Inc standing charge.
Then add our normal electricity average for Feb of ~£84
Sum £204
Our total Feb bill on the Cosy tariff is £169!
That includes £9.04 for the gas range hob, most of which is standing charge 
Ok others savings we shifted dish washing and washing machine use to the cheaper Cosy times but all else remained pretty much the same.
What we’ve noticed.
The house is warmer throughout.
We’ve started heating a largish TV / hifi room annexe on steady state that previously was only heated during its use a few hours a day.
(We use it more now)
Marie (wife) and I are much happier with the constant temperature.
We can quite believe it!
Plus there’s more to come as the tweaks will improve things over the whole of the coming month!
Our months COP was 3.75.
We’ve seen it climb from mid 3s early on to mid 4s and even 6 on a warm couple of days!
It’s very weather dependant of course.
Octopus tell us
We’ve saved
1,210 kg CO2 emissions
So a huge thanks to everyone who helped answer my questions with insight and know-how, not to mention all the great info in general on this site.